Angle sensor

ABSTRACT

The invention pertains to an angle sensor with a fixed stator and a rotor rotating about an axis of rotation, where the stator has several optical-electronic sensor elements, each having the same design, being aligned in a plane vertical to the axis of rotation on a circular line in the perimeter direction concentric to the axis of rotation and being distributed across a range of perimeter angle, where said sensor elements cooperate with the coding provided on the rotor.  
     The objective of the invention with regard to this kind of angle sensor is to solve the technical problem of ensuring that even greater mechanical tolerances, like those occurring in practice, e.g., in the integration of the sensor device into a higher-order structural unit, such as a steering column tube switch module, will not adversely impact dependable operation of the sensor.  
     This problem is solved in that the longitudinal axes of the optical-electronic sensor elements are not aligned radial to the circle line on which these units are positioned in the perimeter direction, but rather are aligned parallel to each other.

DESCRIPTION

[0001] The invention pertains to an angle sensor with a fixed stator and a rotor rotating about an axis of rotation, where the stator has several optical-electronic sensor elements, each having the same design, being aligned in a plane vertical to the axis of rotation on a circular line in the perimeter direction concentric to the axis of rotation and being distributed across a range of perimeter angle, where said sensor elements cooperate with the coding provided on the rotor.

[0002] In particular, the invention pertains to an angle sensor for use in a steering device of a motor vehicle.

[0003] Document EP 774 648 A1 describes an angle sensor of the kind referenced above, with a code ring with n, where n>1, code ring segments having the same geometric design, each having the same coding, where the sensor elements and each code ring segment extend across a range of perimeter angle of 360°/n.

[0004] In the illustrated design example of this kind of sensor device, there are six optical-electronic sensor elements formed as bifurcated light barrier units each having the same spacing from each other and positioned on a perimeter angle range of 72°, where five code ring segments having the same coding, in conjunction with the six sensor elements, produce a one-step, linked, six-bit-code, so that the angular position within a segment can be unambiguously determined.

[0005] The device operates very precisely and dependably in a low-tolerance mechanical structure; however, certain deviations from the ideal configuration, such as a radial offset of rotor and stator with respect to each other, or a deviation of the track formed by the sensor elements from the factory-installed circular line, will allow the device to operate with correct measured results only along a limited perimeter.

[0006] Therefore, the problem of the present invention is to refine this kind of sensor device so that even greater mechanical tolerances can be accepted, such as those required due to the integration of the sensor device into a higher-order structural unit having several components, such as a steering column switch, for example, and/or a volute spring cassette as a kind of steering column tube switch module, and so that still a dependable function of the device will be assured.

[0007] This problem is solved according to this invention, in that the longitudinal axes of the optical-electronic sensor elements (i.e. in the case of the bifurcated light barrier units, for example, the connecting lines between an optical-electronic transmitter and the receiver allocated to it) are not arranged radial to the circular line on which these units are positioned in the perimeter direction, but rather are parallel to each other.

[0008] Favorable embodiments of the invention are indicated in the dependent claims and from the following description of one preferred design example.

[0009] We have:

[0010]FIG. 1 An exploded representation of a state-of-the-art angle sensor

[0011]FIG. 2 A detailed illustration of the arrangement of the optical-electronic sensor element according to this invention, shown in cross section

[0012] The angular sensor according to this invention has essentially the same structure as the state of the art sensor illustrated in FIG. 1. In this case, a stator 1 is secured to the steering unit or to the steering column tube. The stator 1 has a circuitboard 2 which is designed as a segment and which extends across a perimeter angle of 72°=360°/5, and also a ring segment housing 3 aligned on the circuitboard 2 and extending across a perimeter angle of 72° to hold six sensor elements 4; these sensor elements are positioned at equal angular intervals of 12°, and are designed as bifurcated light barrier units. The transmitter elements and receiver elements of the bifurcated light barrier units are contacted directly with the circuitboard 2 and rest opposite each other on different sides of a ring gap 5 which is aligned concentric to the axis of rotation 9 of the steering wheel shaft.

[0013] The sensor elements 4, as is visible in the cut-away illustration of the ring segment housing 3 presented in FIG. 2, have their longitudinal axes (meaning the connecting line between their transmitter and receiver elements) positioned not radial to the circular line, but from the factory-installed circular line, will allow the device to operate with correct measured results only along a limited perimeter.

[0014] Therefore, the problem of the present invention is to refine this kind of sensor device so that even greater mechanical tolerances can be accepted, such as those required due to the integration of the sensor device into a higher-order structural unit having several components, such as a steering column switch, for example, and/or a volute spring cassette as a kind of steering column tube switch module, and so that still a dependable function of the device will be assured.

[0015] This problem is solved according to this invention, in that the longitudinal axes of the optical-electronic sensor elements (i.e. in the case of the bifurcated light barrier units, for example, the connecting lines between an optical-electronic transmitter and the receiver allocated to it) are not arranged radial to the circular line on which these units are positioned in the perimeter direction, but rather are parallel to it.

[0016] Favorable embodiments of the invention are indicated in the dependent claims and from the following description of one preferred design example.

[0017] We have:

[0018]FIG. 1 An exploded representation of a state-of-the-art angle sensor

[0019]FIG. 2 A detailed illustration of the arrangement of the optical-electronic sensor element according to this invention, shown in cross section

[0020] The angular sensor according to this invention has essentially the same structure as the state of the art sensor illustrated in FIG. 1. In this case, a stator 1 is secured to the steering unit or to the steering column tube. The stator 1 has a circuitboard 2 which is designed as a segment and which extends across a perimeter angle of 72°=360°/5, and also a ring segment housing 3 aligned on the circuitboard 2 and extending across a perimeter angle of 72° to hold six sensor elements 4; these sensor elements are positioned at equal angular intervals of 12°. and are designed as bifurcated light barrier units. The transmitter elements and receiver elements of the bifurcated light barrier units are contacted directly with the circuitboard 2 and rest opposite each other on different sides of a ring gap 5 which is aligned concentric to the axis of rotation 9 of the steering wheel shaft.

[0021] The sensor elements 4, as is visible in the cut-away illustration of the ring segment housing 3 presented in FIG. 2, have their longitudinal axes (meaning the connecting line between their transmitter and receiver elements) positioned not radial to the circular line, but between their transmitter and receiver elements) positioned not radial to the circular line, but rather positioned parallel to each other, which causes a significant improvement in device insensitivity to mechanical tolerances caused by radial alignment. The positioning of the sensor elements 4 in this example is chosen as mirror-symmetrical to a diameter line 6 running through the axis of rotation 9.

[0022] A rotor disk is coupled to the steering wheel shaft and is designed as a code ring 7 with five equal, aperture-shaped code ring segments 8 each extending across a perimeter angle of 72°. The code ring segments 8 are moved through the ring gap 5 during the rotation of the code ring 7. The code ring segments 8, in conjunction with the sensor elements 4, generate a one-step, linked code. In the case illustrated here with six light barriers, we will have a six-bit code.

[0023] The one-step, linked code makes possible a precise determination of position, due to progressive counting of the code ring segments 8, even over several rotations of the steering wheel shaft. A reference value is obtained independently of the angle sensor by means of a synchronous measurement of the vehicle wheels, by a rotation of the steering wheel shaft across the entire steering range, or by another initializing method.

[0024] For an unambiguous identification of the code ring segments 8 and thus for an absolute angle measure across one full circular perimeter, the code ring segments 8 can have a different light transmissivity which is measured in analog format by the light barriers. Thus, the particular steering angle can be determined unambiguously and absolutely along the entire circular perimeter of 360°.

[0025] The angle sensor according to this invention is a constituent of a so-called steering column tube switch module, which contains, along with other components, a volute spring cassette. 

1. Angle sensor with a fixed stator (1) and a rotor (7) rotating about an axis of rotation (9), where the stator (1) has several optical-electronic sensor elements (4), each having the same design, being aligned in a plane vertical to the axis of rotation (9) on a circular line in the perimeter direction concentric to the axis of rotation (9) and being distributed across a range of perimeter angle, where said sensor elements cooperate with the coding (7′) provided on the rotor (7), characterized in that the optical-electronic sensor elements (4) have their longitudinal axes aligned parallel to each other.
 2. Angle sensor according to claim 1, characterized in that the optical-electronic sensor elements (4) are positioned mirror-symmetrical to a diameter line (6) running through the axis of rotation (9) and being aligned parallel to it by their longitudinal axes.
 3. Angle sensor according to claim 1 or 2, characterized in that the optical-electronic sensor elements (4) have the same angular spacing from each other.
 4. Angle sensor according to one of claims 1 to 3, characterized in that the stator (1) has a circuitboard (2) aligned vertical to the axis of rotation (9) to hold the optical-electronic sensor elements (4).
 5. Angle sensor according to one of claims 1 to 4, characterized in that the optical-electronic sensor elements (4) are bifurcated light barrier units, and that the coding (7′) is a code aperture ring located in the ring gap (5) formed by these bifurcated light barrier units.
 6. Angle sensor according to one of claims 1 to 4, characterized in that the coding (7′) is a code reflection ring, and that the optical-electronic sensor elements (4) are reflection light barrier units which are positioned opposite the code reflection ring.
 7. Angle sensor according to claim 6, characterized in that the reflection light barrier units are positioned opposite the inner and/or the outer perimeter of the code reflection ring.
 8. Angle sensor according to one of claims 1 to 7, characterized in that the code ring (7′) is equipped with n, where n>1, code ring segments (8) having the same geometric design, and each having the same coding, and that the optical-electronic sensor elements (4) and each of the code ring segments (8) extend across a perimeter angle range of 360°/n.
 9. Angle sensor according to one of claims 1 to 8, characterized in that the code ring (7′) in conjunction with m optical-electronic sensor elements (4) causes a one-step, linked m-bit code.
 10. Angle sensor according to one of claims 1 to 9, characterized in that the perimeter angle range is 360°/5=72°.
 11. Angle sensor according to claim 10, characterized in that six optical-electronic sensor elements (4) are positioned on the perimeter angle region.
 12. Use of an angle sensor according to one of the preceding claims in a steering device of a motor vehicle, characterized in that the stator (1) is mounted, rotation-tight, to the steering column of the steering device, and that the rotor (7) surrounding the code ring (7′) is joined rotation-tight to the steering wheel shaft of the steering device. 